The invention relates to a laser system and, more particularly, to a method of using a laser system to control fluence and power density at a target to minimize thermal loading of the target.
Machining of electronic component material using a laser is a function of the laser parameters and the machining characteristics of the specific material. The machining characteristics are substantially affected by the thermal properties of the material or of the material sets forming conductive layers and dielectric layers. Excess thermal loading of materials can cause quality and reliability problems with the final product.
Conventionally, the modulation of fluence and power density (peak power density) of a laser system to affect thermal loading is achieved by varying the power output of the laser, attenuating the power, varying the repetition rate of the laser, or changing the position of the workpiece in relation to the focal plane of the respective laser system. These methods have distinct disadvantages in controlling the fluence and or power density at the target or workpiece. For example, changing the repetition rate of the laser will cause instability and lead to a certain predetermined set of conditions. The entire range of desired fluence and power density settings cannot be scanned. In addition, the repetition rate cannot be used to create changes in less than one second intervals for a given laser source due to the resonator instability and first pulse phenomena. Thus, changing the repetition rate of the laser tends to introduce a large amount of variability in the fluence and power density.
Accordingly, there is a need to provide a method of minimizing thermal loading to surrounding areas while machining an electronic component material using a laser.
An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing a method of controlling thermal loading of an electronic component material during ablation thereof. The method provides a first laser light beam at a certain power density and fluence and uses the first laser light beam to remove a portion of a first side of the material. A second laser light beam is provided at a certain power density and fluence and the second laser light beam is used to remove a portion of a side of the material opposing the first side thereof substantially simultaneously as the portion of the first side is being removed.
In accordance with another aspect of the invention, a method of controlling thermal loading of an electronic component material during ablation thereof includes directing a laser light beam to remove material so as to create a heat affected zone in the material. The operator then waits a certain time period to permit the material to cool and to permit the heat affected zone to expand in the material. Thereafter, the laser light beam is directed to further remove material in at least a portion of the heat-affected zone.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.